1. Technical Field
The present invention generally relates to an apparatus and method for forming a surface film, and more particularly, to an apparatus and method for performing a non-plasma chemical reaction to form the surface film.
2. Background Art
The ability to control etching by hydrogen fluoride (HF) to a given thickness of a surface layer of a workpiece that has been adapted for etching is an important prerequisite for accurate etching in the manufacture of an integrated circuit (IC). The surface layer of the workpiece may be adapted for etching by forming a surface layer that is an oxide of the material of the workpiece. If the workpiece comprises silicon or germanium, the surface layer of the workpiece may be adapted for etching by forming the surface layer of silicon dioxide (SiO2) or germanium dioxide (GeO2). Pure hydrogen fluoride (HF) may etch the adapted surface layer by forming gaseous silicon tetrafluoride (SiF4). The gaseous SiF4 is very volatile such that exposing the surface layer to HF readily etches the surface layer, thereby exposing a remaining layer of oxide to etching by the HF. Etching to the given thickness is difficult to control because the formation of SiF4 continues until the surface layer, i.e., the oxide layer, has been completely etched due to formation and evaporation of SiF4.
In view of the need to control the etching thickness when the adapted surface layer of a workpiece is exposed to HF, there is a need for an apparatus and method that provides controlled etching of the adapted surface layer with HF.